A Rare ABCB5 Variant in a Familial Case of Intrahepatic Cholestasis of Pregnancy: A Potential Novel Genetic Contributor

Background/Objectives: Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder with a multifactorial pathogenesis and a well-established genetic component. While pathogenic variants in genes such as ABCB4 and ABCB11 are implicated in a subset of cases, many remain genetically unexplained. This study aimed to investigate the genetic background of ICP in a multi-generational family with recurrent hepatobiliary disease. Methods: Whole-exome sequencing was performed on the proband and five female relatives. Variant filtering prioritized rare, exonic or splice-site variants predicted to undergo damage by in silico tools and which were present in all affected family members. Identified variants were assessed using population databases and compared with a control group of 433 unrelated women with uncomplicated pregnancies. Variant confirmation was performed using Sanger sequencing and high-resolution melting analysis. Results: No pathogenic variants were identified in known ICP-associated genes. However, a rare heterozygous missense variant in ABCB5 (c.1610G>A; p.Arg537His; rs779950110) was found in all affected individuals and two younger female relatives. This variant is exceedingly rare in population databases, absent in controls, and predicted to be pathogenic by multiple algorithms. ABCB5, although not previously linked to ICP, is an ATP-binding cassette transporter expressed in various tissues, including liver compartments. Conclusions: This study reports a novel ABCB5 variant segregating with ICP and early-onset hepatobiliary disease in a family. These findings suggest ABCB5 as a potential new susceptibility gene in ICP, warranting further functional investigation.